“The Severance did what it was meant to,” Hierophant said. “It cut both his body and his soul.”

...

“Then what does the Severance even do?” the Mirror Knight harshly said.

“It destroyed him,” Hierophant informed him. “You did sufficient damage to disperse his soul. Only instead of moving on his soul remained bound to its anchor, and then something-”

“An aspect,” I elaborated. “Return.”

“An aspect,” Hierophant adjusted, “ensured that it formed anew. The scar the Severance left is still there, the damage done was permanent.”

“So the only way to destroy him is to destroy every single fragment of his soul with the Severance,” the White Knight evenly said.

- Book 7, Chapter 67: And Justice For All (Redux)